1. Field of the Invention
The present invention relates to devices used to restrain the movement of a cable that is disposed within a conduit and, more particularly, to cable anchors used within coiled tubing to suspend an electric submergible pumping system within a wellbore.
2. Description of Related Art
To reduce the size of equipment and the associated costs needed to deploy and recover an electric submergible pumping system ("ESP"), ESP's can be suspended from coiled tubing, rather than conventional jointed tubing. This method takes advantage of the relatively low cost and ease of transportation of the units used to install and remove coiled tubing. A typical arrangement for suspending an ESP on coiled tubing is disclosed in U.S. Pat. Nos. 3,835,929; 4,830,113; and 5,180,014.
The cable that is used to connect the ESP to a surface power source does not have sufficient internal strength to support its own weight over about 60 to 200 feet. Therefore, the cable is clamped, banded or strapped to the jointed tubing or the coiled tubing at intervals of about every 50 to 150 feet, as disclosed in U.S. Pat. No. 4,681,169. Alternatively, the cable can be encased within the coiled tubing, as disclosed in U.S. Pat. Nos. 4,336,415; 4,346,256; 5,145,007; 5,146,982; and 5,191,173.
When the cable is encased within the coiled tubing, standoff devices can be used to centralize the cable within the coiled tubing to permit fluid production through the coiled tubing. These standoff devices also support the cable, in place of the external clamps or straps, by preventing longitudinal movement of the cable with respect to the coiled tubing and thereby transfer the weight of the cable to the coiled tubing. These standoff devices are usually referred to as "cable anchors", and are disclosed in U.S. Pat. Nos. 5,193,614; 5,269,377; and 5,435,351.
Common problems associated with the prior cable anchors are that such cable anchors are either (i) relatively mechanically complex, and require injection of a solvent to release the anchors, or (ii) require a time consuming and uncontrollable chemical interaction to cause elastomeric materials to swell. There is a need for a simple mechanical cable anchor assembly that is quickly and predictably operable, and is not dependent upon the uncertain nature of chemical interactions and solvents.